Algorithms: Array Techniques Tutorials and Code Examples - Page 14

Prefix Sum Range Query in C#

Prefix sums turn a range sum into a subtraction.

csharp

    static int range_sum(ReadOnlySpan<int> a, int left, int right) {
        checked {
            int n = a.Length;
            alg_require(((n >= 0) && (n <= 1000000)));
            alg_require((a.Length == n));
            alg_require(((left >= 0) && (left <= right) && (right < n)));
            int[] prefix = new int[alg_size((n + 1))];
            int i = 0;
            while ((i < n)) {
                prefix[(i + 1)] = (prefix[i] + a[i]);
                i = (i + 1);
            }

Nov 15, 2026 csharp

Algorithms: Array Techniques

Prefix Sum Range Query in C++

Prefix sums turn a range sum into a subtraction.

cpp

int range_sum(const std::vector<int>& a, int left, int right) {
    alg_require(a.size() <= 1000000);
    int n = (int)a.size();
    alg_require(((n >= 0) && (n <= 1000000)));
    alg_require(((int)a.size() == n));
    alg_require(((left >= 0) && (left <= right) && (right < n)));
    std::vector<int> prefix(alg_size(alg_add(n, 1)), 0);
    int i = 0;
    while ((i < n)) {
        prefix[alg_add(i, 1)] = alg_add(prefix[i], a[i]);
        i = alg_add(i, 1);
    }

Nov 15, 2026 C++

Algorithms: Array Techniques

Prefix Sum Range Query in C

Prefix sums turn a range sum into a subtraction.

c

int range_sum(const int *a, size_t a_length, int left, int right) {
    int alg_error = 0;
    int alg_result = INT_MIN;
    errno = 0;
    int *prefix = NULL;
    if (a_length > 1000000 || (a_length && !a)) { errno = EINVAL; alg_result = INT_MIN; goto alg_cleanup; }
    int n = (int)a_length;
    if (alg_error) { errno = ERANGE; alg_result = INT_MIN; goto alg_cleanup; }
    if (!(((n >= 0) && (n <= 1000000)))) { errno = EINVAL; alg_result = INT_MIN; goto alg_cleanup; }
    if (alg_error) { errno = ERANGE; alg_result = INT_MIN; goto alg_cleanup; }
    if (!(((int)a_length == n))) { errno = EINVAL; alg_result = INT_MIN; goto alg_cleanup; }
    if (alg_error) { errno = ERANGE; alg_result = INT_MIN; goto alg_cleanup; }

Nov 15, 2026 C

Algorithms: Array Techniques

Prefix Sum Range Query in JavaScript

Prefix sums turn a range sum into a subtraction.

javascript

function range_sum(a, left, right) {
    alg_require(a instanceof Int32Array);
    alg_require(Number.isInteger(left) && left >= -2147483648 && left <= 2147483647);
    alg_require(Number.isInteger(right) && right >= -2147483648 && right <= 2147483647);
    let n = a.length;
    alg_require(((n >= 0) && (n <= 1000000)));
    alg_require((a.length == n));
    alg_require(((left >= 0) && (left <= right) && (right < n)));
    let prefix = new Int32Array(alg_size(alg_add(n, 1)));
    let i = 0;
    while ((i < n)) {
        prefix[alg_add(i, 1)] = alg_add(prefix[i], a[i]);

Nov 15, 2026 javascript

Algorithms: Array Techniques

Prefix Sum Range Query in Java

Prefix sums turn a range sum into a subtraction.

java

    static int range_sum(int[] a, int left, int right) {
        java.util.Objects.requireNonNull(a, "a");
        int n = a.length;
        alg_require(((n >= 0) && (n <= 1000000)));
        alg_require((a.length == n));
        alg_require(((left >= 0) && (left <= right) && (right < n)));
        int[] prefix = new int[alg_size(Math.addExact(n, 1))];
        int i = 0;
        while ((i < n)) {
            prefix[Math.addExact(i, 1)] = Math.addExact(prefix[i], a[i]);
            i = Math.addExact(i, 1);
        }

Nov 15, 2026 Java